The devices using an optical disk, a magnetic tape, or other forms of media are known as data storage devices. Among them, a hard disk drive (HDD) is commonly used as a storage device for a computer, and the HDD is one of storage devices essential for computer systems which are currently used. In addition, the use of the HDD are not only limited to computer systems but also has widely expanded because of the superior characteristics. The HDDs are used, for example, for moving picture recording/reproducing devices, car navigation systems, cellular phones, removable memories used for digital cameras and the like.
The HDD is provided with a magnetic disk for storing data and a head for writing and/or reading out data to/from the magnetic disk. The head has a head element portion which is a thin film element and a slider with the head element portion disposed on its surface. The head element portion has a write element portion which converts an electric signal into a magnetic field in accordance with data to be recorded onto the magnetic disk and a read element portion which converts a magnetic field provided from the magnetic disk into an electric signal. Typically, the write element portion and the read element portion are formed integrally in one thin film element.
The HDD is further provided with an actuator for moving the head to a desired position over the magnetic disk. The actuator is driven by a voice coil motor (VCM) and is adapted to pivot about a pivot shaft, thereby moving the head radially over the magnetic disk which is rotating. With this movement, the head accesses to a desired track formed on the magnetic disk, whereby it is possible to read or write data.
The loading/unloading type HDD is provided with a ramp for retraction of the head from above the surface of the magnetic disk. The ramp is disposed in proximity to an outer periphery end of the magnetic disk. When the rotation of the magnetic disk stops, the head is attracted to the disk surface. To avoid this inconvenience, when the rotation of the magnetic disk stops, the actuator causes the head to be retracted to the ramp from the recording surface of the magnetic disk.
The actuator has a suspension and an arm for supporting the head. A tab is provided at a front end portion of the suspension. As the tab is guided to the ramp, the head retracts to the outside from above the surface of the magnetic disk and thus unloading is performed. Conversely, as the tab leaves the ramp, the head moves from the outside of the magnetic disk to a position above the disk surface and thus loading is performed.
FIG. 9 is a side view of a load beam 910 provided at a front end portion of a suspension, which is used in a conventional HDD. FIG. 9 shows the state of the load beam 910 with a head 905 positioned over a magnetic disk 901.
As shown in the same figure, the head 905 is supported at one point by a dimple 960 provided on the load beam 910 and is flying at a predetermined height over a surface of the magnetic disk 901. A tab 916 is bent and extends away from the magnetic disk 901 from a front end of the load beam 910. That is, over the magnetic disk 901, the tab 916 is formed so as to be higher than a head support portion 961 of the load beam 910. In particular, the tab 916 extends in the same direction as the extending direction of the load beam 910 (head support portion 961). In other words, in a state in which the head 905 flies over the magnetic disk 901, the inclination of the load beam 910 (head support portion 961) and that of the tab 916 relative to the surface of the magnetic disk 901 are almost the same.
FIG. 10 shows loading and unloading conditions as seen from the front end side of the conventional load beam 910 and FIG. 11 shows loading and unloading conditions as seen from a side face of the conventional load beam 910.
During unloading, as shown in FIG. 10, the tab 916 slides on a sliding surface 800 of a ramp 915, thereby lifting the load beam 910 up to a predetermined height and separating the head 905 from the magnetic disk 901. At this time, the tab 916 first comes into contact with a magnetic disk-side inclined surface 801 of the sliding surface 800 and slides thereon and rises up to a maximum lift surface 802. In the same figure, the numeral 901a represents a position at which the tab 916 first comes into contact with the slant face 801 of the magnetic disk and numeral 901b represents a position at which the tab 916 is required to be lifted up to separate the head 905 from the magnetic disk 901. The height H in the figure represents a lift quantity for lift up to the height necessary for separation of the head 905 from the magnetic disk 901.
During loading or unloading, as shown in FIG. 11, a corner 915a of the sliding surface of the ramp 915 and part of an abdominal surface 916a of the tab 916 come into contact with each other, while a front end 916b of the tab 916 is away from the sliding surface 800. The position and size of the ramp 915 vary due to a mechanical error. Here, only errors of the ramp mounting position (in the direction of the suspension pivot shaft) are considered without considering errors in the ramp height direction. For example, errors of the ramp mounting position include an actuator mounting error and a ramp mounting error.
FIG. 11(a) shows the case where there is no mounting position error of the ramp 915, FIG. 11(b) shows the case where a side face 915b on the load beam 910 side of the ramp 915 is close to the load beam 910, and FIG. 11(c) shows the case where the side face 915b on the load beam 910 side of the ramp 915 is distant from the load beam 910.
In FIG. 11(a), the corner 915a of the ramp 915 and a portion near the center of the abdominal surface 916a of the tab 916 are in contact with each other. In FIG. 11(b), the corner 915a of the ramp 915 and the front end side of the abdominal surface 916a of the tab 916 are in contact with each other because the side face 915b of the ramp 915 is distant from the load beam 910. In FIG. 11(c), the corner 915b of the ramp 915 and the root side of the abdominal surface 916a of the tab 916 are in contact with each other because the side face 915b of the ramp 915 is close to the load beam 910. That is, the point of contact between the ramp 915 and the tab 916 is the position of the corner 915a and the position of contact between the ramp 915 and the tab 916 differs due to an error of the mounting position of the ramp 915. Therefore, taking the error of the mounting position of the ramp 915 into account, the tab 916 is required to have such a length to reach the ramp 915 even at the farthest position of the ramp from the load beam.
Taking into account the inclination of the load beam 910 relative to the magnetic disk 901 in a lifted state of the load beam, it is assumed that the inclination of the load beam 910 in FIG. 11(a) is θ1, the inclination of the load beam 910 in FIG. 11(b) is θ2, and the inclination of the load beam 910 in FIG. 11(c) is θ3. As a result, the position of contact between the tab 916 and the ramp 519, i.e., the position at which the tab 916 is lifted, differs in the respective cases and the relationship of θ2<θ1<θ3 is established.
If the inclination of the load beam 910 during loading and unloading varies due to an error of the mounting position of the ramp 915, the position (901b in FIG. 10) at which the head 905 is separated from the magnetic disk 901 varies during unloading. For example, as shown in FIG. 11(b), if the inclination of the load beam 910 is small because the corner 915a of the ramp 915 is distant from the load beam, the position at which the head is separated during unloading becomes distant from the center of the magnetic disk. As shown in FIG. 11(c), if the inclination of the load beam 910 is large because the corner 915a of the ramp 915 is close to the load beam, the position at which the head is separated during unloading becomes close to the center of the magnetic disk.
Thus, the range of the recording area of the magnetic disk is determined by the position 901b at which the head is separated, so if the position 901b changes due to an error of the mounting position of the ramp 915, the recording area of the magnetic disk also changes. Therefore, also as to the recording area of the magnetic disk, it is necessary to take an error of the ramp mounting position into account and establish, as an effective recording area, a range of a narrow recording area wherein the ramp is the closest to the load beam.
To lift the load beam up to a required height to ensure the recording area of the disk irrespective of an error of the ramp mounting position, it is necessary to heighten the ramp. However, such an increased height of the ramp becomes a restriction on the thickness of the magnetic disk drive. Moreover, since the length from the point of contact between the tab and the ramp up to the front end of the tab varies due to an error of the ramp mounting position, the height up to the front end of the tab is not constant in the state where the tab and the ramp are in contact with each other. Therefore, as shown in FIG. 11(c), it is necessary to take into account the case where the ramp and the root side of the tab are put in contact with each other. This also becomes a restriction on the thickness of the magnetic disk drive.
In Patent Literature 1 (Japanese Patent Laid-Open No. 2005-71588), a projecting portion for contact with a ramp is formed at a front end of a tab in order to decrease the contact area between the tab and the ramp. However, this does not intend to increase the memory capacity of a magnetic disk or reduce the thickness of a magnetic disk drive. Besides, since the tab described in Patent Literature 1 extends as a plate tab to a front end of a load beam, it is apt to deflect upon contact of its projecting portion with the ramp, thus giving rise to a problem in point of rigidity of the tab.
Further, as shown in FIG. 10, the width of the conventional tab 916 is smaller than that of the head support portion 961 of the load beam 910. The conventional tab 916 extends from the center of the front end of the load beam 910 so as to be U-shaped cross-sectionally in the transverse direction (this is also the case with Patent Literature 2 (Japanese Patent Laid-Open No. 2005-11511)). Consequently, during unloading, the magnetic disk-side inclined surface 801 of the ramp 915 and the center of the tab 916, i.e., the center of the load beam 910, come into contact with each other. For example, there is the case where the position of the head 905 upon initial contact between the tab 916 and the ramp 915 during unloading is to be set on the central side of the magnetic disk or the case where the contact point 901a between the tab 916 and the ramp 915 is to be set closer to the outer periphery of the magnetic disk.
In this case, conventionally, the tab 916 is provided asymmetrically with respect to the center in the transverse direction of the load beam 910. Alternatively, as in Patent Literature 3 (Japanese Patent Laid-Open No. 11-250603), the point of contact between the tab and the ramp is rendered oblique relative to a central axis of a suspension. If the tab is formed asymmetrically or the point of contact between the tab and the ramp is rendered oblique, a large vibration occurs due to a twist during loading or unloading, thus resulting in that dynamic characteristics of the suspension including the load beam are deteriorated markedly.
In Patent Literature 4 (Japanese Patent Laid-Open Publication No. 8-221922), a front end of a suspension is symmetric and a flange portion is provided in part of the outer periphery of the front end of the suspension, which flange portion is put in contact with a ramp (lift portion). In this case, since the flange portion is provided only at the portion to be contacted with the ramp, it is impossible to prevent vibration caused by a twist during loading or unloading.
Thus in the conventional HDD, the head support portion of the load beam and the tab extend in the same direction and a corner of the ramp and the abdominal surface of the tab come into contact with each other at the time of loading or unloading. Therefore, the tab length and the recording area of the magnetic disk obtain restrictions due to an error of the ramp mounting position, thus giving rise to the problem that it is difficult to increase the memory capacity of the magnetic disk or reduce the thickness of the magnetic disk drive.
Moreover, in the conventional HDD, when the initial point of contact with the tab and the ramp during unloading is set outside the disk, the tab is made asymmetric, or the point of contact with the tab and the ramp is made oblique, or a flange portion is provided only at the portion of contact with the ramp, thus giving rise to the problem that the rigidity of the tab and dynamic characteristics of the suspension are deteriorated.